Wafer level packaging (WLP) is the technology of packing an integrated circuit (IC) at wafer level, resulting in a device substantially having the size of the die. The traditional WLP technology includes the Fan-In WLP (FIWLP) technology which forms a dense peripheral array of contact pads at the edge of the chip and a redistribution layer (RDL) is added to route connection/circuit traces to a less dense area array. However, due to the configuration of inputs/outputs (I/Os) which are limited to the surface of the die, FIWLP packages are limited to low-end semiconductor devices, e.g., devices requiring less than 300 I/Os.
Fan-out WLP (FOWLP) technology, such as the Embedded Wafer Level Ball Grid Array (eWLB), is an enhancement of the FIWLP technology that provides a solution for semiconductor devices requiring a greater number of I/Os and a higher level integration. For example, FOWLP technology selects pre-diced known good dies (KGDs), reconstitutes the KGDs using am epoxy mould compound (EMC) into a wafer or panel for providing additional space for interconnects and adds a fan-out redistribution layer (RDL) having a dielectric layer and copper interconnects. Any number of additional interconnects can be realized on the package in an arbitrary distance (i.e., a fan-out design) as opposed to FIWLP, where the chip area would not be sufficient to place the required number of interconnects at a suitable distance.
In order to meet electrical performance requirements of semiconductor devices, the RDL is constructed using low-k or ultra low-k dielectric materials along with copper interconnects. However, such a material choice inevitably deteriorates the mechanical strength of the package, causing chip package interaction (CPI) reliability issues. Examples of CPI reliability issues include delamination from die corners and crack propagation from the area where dicing tool cuts the wafer into the active chip areas.
Therefore, it is desirable to provide simplified and cost efficient techniques for mitigating the CPI reliability issues.